Why Is the Water Temperature Below Threshold Yet the Boiler Won't Fire?

Resets

• If your boiler has recently triggered the limit switch through an accident, the boiler control panel could be running into problems starting the boiler again. It has just received a command signal to shut down the burner, and fixing the temperature problem might not restore proper function. Boilers have a reset button you can push to fully restart the system and clear up any electrical confusion. Do not push the reset button more than three times or you could lock out your system complete, which requires professional work.

Sensor Problems

• Most boilers have two different sensors, one on the bottom near the burner and one at the top of the tank. These sensors are not perfect. They can fail because of electrical problems or become dislodged and stop reading temperatures accurately. This will keep the boiler from starting properly because the control panel cannot receive the right information. Re-attaching or replacing these sensors can fix the problem and restore function.

Air Problems

• If your boiler uses fuel, then it needs access to a steady supply of air for combustion. If your air vent becomes clogged, the burner will start operating strangely. It will produce a weak flame, a lot of soot, and might shut down altogether. You can fix this problem by checking your air filter and supply air vent for any blockages. Anything from leaves and dirt to snow in the winter can cut off boiler air and prevent the burner from working.

Ignition Problems

• Sometimes burners are working correctly but cannot get the ignitor to light their fuel. When this happens, the ignitor will try several times and then shut down the burner automatically so fuel does not build in the combustion chamber. Adjusting the ignitor can solve this problem, but if the ignitor doesn't work at all it might need to be replaced.